Commit 844cf763 authored May 11, 2017 by Jon Paul Maloy Committed by David S. Miller May 11, 2017

tipc: make macro tipc_wait_for_cond() smp safe

The macro tipc_wait_for_cond() is embedding the macro sk_wait_event()
to fulfil its task. The latter, in turn, is evaluating the stated
condition outside the socket lock context. This is problematic if
the condition is accessing non-trivial data structures which may be
altered by incoming interrupts, as is the case with the cong_links()
linked list, used by socket to keep track of the current set of
congested links. We sometimes see crashes when this list is accessed
by a condition function at the same time as a SOCK_WAKEUP interrupt
is removing an element from the list.

We fix this by expanding selected parts of sk_wait_event() into the
outer macro, while ensuring that all evaluations of a given condition
are performed under socket lock protection.

Fixes: commit 365ad353 ("tipc: reduce risk of user starvation during link congestion")
Reviewed-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent ad990dbe

net/tipc/socket.c

+19 −19

Original line number	Diff line number	Diff line
		@@ -362,22 +362,22 @@ static int tipc_sk_sock_err(struct socket sock, long timeout)
		return 0;
		}

		#define tipc_wait_for_cond(sock_, timeout_, condition_) \
		#define tipc_wait_for_cond(sock_, timeo_, condition_) \
		({ \
		int rc_ = 0; \
		int done_ = 0; \
		struct sock *sk_; \
		int rc_; \
		\
		while (!(condition_) && !done_) { \
		struct sock *sk_ = sock->sk; \
		while ((rc_ = !(condition_))) { \
		DEFINE_WAIT_FUNC(wait_, woken_wake_function); \
		\
		rc_ = tipc_sk_sock_err(sock_, timeout_); \
		sk_ = (sock_)->sk; \
		rc_ = tipc_sk_sock_err((sock_), timeo_); \
		if (rc_) \
		break; \
		prepare_to_wait(sk_sleep(sk_), &wait_, \
		TASK_INTERRUPTIBLE); \
		done_ = sk_wait_event(sk_, timeout_, \
		(condition_), &wait_); \
		prepare_to_wait(sk_sleep(sk_), &wait_, TASK_INTERRUPTIBLE); \
		release_sock(sk_); \
		(timeo_) = wait_woken(&wait_, TASK_INTERRUPTIBLE, (timeo_)); \
		sched_annotate_sleep(); \
		lock_sock(sk_); \
		remove_wait_queue(sk_sleep(sk_), &wait_); \
		} \
		rc_; \

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